"Gourdin - Rectangular Graphometer - 1781"
GOURDIN (Pierre) Rectangular graphometer dated 1781Unusual shape for a French brass graphometer from the 18th century. It is signed and dated "Gourdin au Quart de cercle à Paris 1781".This graphometer is rectangular, equipped with two water levels, two fixed pinnules and an alidade with two pinnules.On the back, it shows no trace of a ball joint or support.It was therefore used directly placed on the board or perhaps hung from the side on the board.Thus, the two levels were used to put the instrument perfectly flat.We could not find any other similar graphometer, in the old or modern literature.The condition is excellent. The size is 19×11.8 cm 
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